1. Field of the Invention
The present invention relates to semiconductor memory devices.
2. Description of the Prior Art
Heretofore, in the inspection of a semiconductor memory device, such as DRAM (dynamic RAM), for operability, an examination consisting of applying the write-in and readout of information for testing purposes to individual elements of such a device has been used.
The influence of such examination time on productivity, which is of limited impact for devices of relatively small memory capacity, becomes more and more important with increasing memory capacity. Currently, the enhanced memory capacity of a semiconductor memory device has resulted in the time taken for testing the operability of such a memory device to assume a high degree of significance in its effect on productivity. For example, it is said to take at least 1 minute for examining every 4 Mbit DRAM by a conventional technique, which indicates that testing procedure relying upon the testing of individual elements in separate stages cannot meet productivity demand from the viewpoint of mass production of semiconductor memory devices extremely large memory capacities.